Heretofore there has been a great deal of development work in anti-skid systems for vehicles, and especially for aircraft. Many patents have been issued on different types of anti-skid apparatus and controls to endeavor to provide maximum braking capacity for the vehicle but at the same time to limit or prevent skid conditions from existing or being maintained. In these various commercial anti-skid systems and apparatus provided heretofore, it has usually been the practice to dump or release the fluid in the brake system for a skidding wheel into a reservoir and then resupply brake fluid when braking conditions are to be re-established. Usually the dumping of the hydraulic fluid in the brake pressure system causes a loss of position of the brake pedal which is not then in a full pressure producing position and the pedal needs to be depressed further to provide braking pressures. Or, in other words, such a quantity of brake pressure liquid has been dumped by brake pressure release that some appreciable pedal movement or time interval is involved in pressure reapplication. Naturally, any time loss in braking action is quite objectionable.
Furthermore, prior anti-skid systems of all types have been relatively expensive even when provided for small aircraft or other small vehicles.
With various advances in the anti-skid control art, the systems for preventing, eliminating or controlling anti-skid conditions have become more and more complex and have usually required sophisticated electronic controls. Examples of such systems are found in U.S. Pat. Nos. 3,856,365 and 3,880,475, but many other patents have been granted on anti-skid systems and on components thereof, such as U.S. Pat. Nos. 3,286,734; 3,443,594; and 3,486,801 on valves for use in anti-skid brake systems.
It is the general object of the present invention to provide an improved anti-skid control system utilizing an anti-skid power valve means therein, which valve means will release or remove only a portion of the pressure liquid in the brake system or means for a wheel having a skid condition existing thereon and to maintain hydraulic pressure fluid at reduced pressure in operative association with such wheel brake system.
Another object of the invention is to eliminate any full release of brake action or pressure liquid in correcting an anti-skid or skid condition.
Another object of the invention is to maintain brake pedal position in a brake system controlling a wheel having skid conditions existing therein and to signal the operator when relieving such skid producing braking pressure.
Yet another object of the invention is to provide a relatively simple, inexpensive, uncomplicated substantially mechanical apparatus for controlling skid conditions in a wheel and for removing the skid conditions without complete dumping of all pressure liquid in such wheel brake system.
Another object of the invention is to provide two mechanical controls in an anti-skid system that can be independently varied or be varied in correlation with each other for control of anti-skid and braking action.
The foregoing and other objects and advantages of the present invention will be made more apparent as the specification proceeds.